An equine veterinarian says there is an extremely high risk of more horses contracting the Hendra virus at Lowood in the Brisbane Valley in Queensland.

One horse has died of the bat-borne disease, and up to 20 others from the same property are being tested.

Four people had minimal contact with the sick animal but are not deemed to be at risk.

But veterinarian Dr Louise Cosgrove says it is likely more horses will become infected and warns it can take up to a month for a Hendra vaccine to take effect.

"With the area in Lowood, there is actually a colony of bats that live along the river out of Lowood towards Fernvale, so it's an extremely high possibility that there will be more Hendra cases in the area," she said.

"It takes 42 days for the horses to be completely vaccinated against Hendra, so while owners are waiting for the vaccine to give the protection, they really need to be vigilant with their minimisation of contamination.

"So not feeding their horses under trees and taking their waters out from under trees and things like that."

Chief biosecurity officer Dr Jim Thompson warns Hendra can occur at any time of the year, not just in winter.

"We don't like to call it Hendra season, we've had enough cases outside what is the middle of winter period to suggest that people can get a bit complacent if they think there is a Hendra season," he said.

"There is no doubt we've had more cases in the June-to-September period than the rest of the year, but Hendra is around all the time so it can be any time of the year."

The Queensland Horse Council says the latest outbreak of Hendra highlights the need to vaccinate horses.

"We have a vaccine for horses that is very effective against the disease so in effect we need to learn that we've been given the option to vaccinate our horses," said council president Debbie Dekker.